1. Field of the Invention
The present invention generally relates to a system for preventing a fuel evaporation gas from scattering, and particularly relates to a self-diagnosis apparatus in such a fuel evaporation gas scattering preventing system.
2. Description of the Related Art
Conventionally, known is a system for preventing a fuel evaporation gas generated in a fuel tank from scattering into the atmosphere. For example, in the system as disclosed in Japanese Patent Unexamined Publication No. JP-A-57-129247 has a configuration in which a fuel evaporation gas generated in a fuel tank is absorbed by an absorption material in a canister and the thus absorbed fuel evaporation gas is led into a suction manifold, by means of negative pressure in the suction manifold, together with fresh air sucked through an atmosphere opening hole of the canister, in accordance with an engine operating condition.
In such a conventional system, however, there has been such a possibility that if a discharge path connecting the canister and the suction manifold to each other is crushed or blocked for some reasons to thereby be closed, the canister is fulfilled with the fuel evaporation gas and then the fuel evaporation gas is scattered into the atmosphere through the atmosphere opening hole of the canister. Further, there has been such a possibility that if the discharge path to the suction manifold is damaged or the piping of the discharge path comes off for some reasons so that the discharge path is opened to the atmosphere, the fuel evaporation gas is scattered from the canister into the atmosphere. Moreover, if the atmosphere opening hole of the canister is closed for some reasons, there has been such a possibility that the inner pressure in the canister is raised because of the fuel evaporation gas generated in the fuel tank so that the piping comes off, and so that the fuel evaporation gas is scattered into the atmosphere.